XPath is a W3C specification for locating
nodes in an XML document. It provides an expression syntax that can
determine a node based on its type, location, and relation to other
nodes in a document. XPath is generally not useful alone, but works
in conjunction with other tools, especially XSLT. Figure 45-1 shows the types in this namespace.
evaluate expressions and match nodes in XML documents.
XPathDocument is a document object designed to
provide fast document navigation through XPath and is used by the
System.Xml.Xsl classes for XSLT transformations.
XPathNavigator is the core entry point for doing
XPath expressions; it is abstract, allowing for more than just XML
documents to be XPath-navigated. For example, an ADO.NET provider
could, if it desired, implement the
IXPathNavigable interface and return an
XPathNavigator that translated XPath queries into
a SQL SELECT statement. (See Aaron Skonnard's MSDN
Magazine article "Writing XML Providers for
Microsoft .NET" for more details about using
XML-based technologies over data sources other than XML documents.)